Two phase oil cooling system

ABSTRACT

The present disclosure provides a two phase oil cooling system for a work vehicle. The system includes a condenser, an evaporator, a refrigerant path, and a pump. The condenser cools a refrigerant from vapor form to liquid form. The evaporator exchanges heat between a first fluid of the work vehicle and the refrigerant, and heats the refrigerant from liquid form to vapor form. The refrigerant path comprises a first refrigerant path thermally coupling the condenser to the evaporator and a second refrigerant path thermally coupling the evaporator to the condenser. The refrigerant flows through the refrigerant path. The pump is positioned in the first refrigerant path for pumping the refrigerant from the condenser to the evaporator, such that the evaporator is downstream of the pump and the condenser is downstream of the evaporator.

RELATED APPLICATIONS

N/A

FIELD OF THE DISCLOSURE

The present disclosure relates generally to a cooling system applied to a work vehicle.

BACKGROUND OF THE DISCLOSURE

The off-highway industry uses a variety of rotating components: transmissions, axles, e-machines, hydraulic pumps and motors, etc. These components may use oil as a working fluid and/or for lubrication and cooling. A rotating component of a work vehicle, such as axle or transmission, generates heat while in operation. Conventionally, the heat is partially removed by a cooling system/circuit, including a radiator coupled to the work vehicle, a cooling fan, and an oil path. A hot cooling oil from the rotating component flows into the radiator and is cooled by the radiator due to the cooling fan providing an air flow passing through a series of heat dissipation components of the radiator. The cooled cooling oil later flow back to the rotating component. However, since the oil is typically pumped outside the rotating component to the remote single phase oil-to-air heat exchanger for cooling, this cooling circuit is prone to leaks, contamination, pumping losses and has a low heat transfer coefficient.

SUMMARY OF THE DISCLOSURE

The present disclosure includes a two phase oil cooling system that leverages the advantages of two-phase refrigerant applied on oil cooling which has significantly higher heat transfer coefficient. In addition, the present disclosure has the advantage of distributed heat loads from several components and does not require that oil be pumped to a remote cooling system.

According to an aspect of the present disclosure, a two phase oil cooling system is provided for a work vehicle. The two phase oil cooling system includes a condenser, an evaporator, a refrigerant path, and a pump. The condenser cools a refrigerant from vapor form to liquid form. The evaporator exchanges heat between a first fluid of the work vehicle and the refrigerant, thereby heating the refrigerant from liquid form to vapor form. The refrigerant path comprises a first refrigerant path thermally coupling the condenser to the evaporator and a second refrigerant path thermally coupling the evaporator to the condenser. The refrigerant flows through the refrigerant path. The pump is positioned in the first refrigerant path for pumping the refrigerant from the condenser to the evaporator, such that the evaporator is downstream of the pump and the condenser is downstream of the evaporator.

According to another aspect of the present disclosure, a two phase oil cooling system is provided for a work vehicle. The two phase oil cooling system includes a condenser, an evaporator, and a refrigerant path. The condenser cools a refrigerant from vapor form to liquid form. The evaporator is positioned below the condenser and exchanges heat between an oil of a rotating component of the work vehicle and the refrigerant, thereby heating the refrigerant from liquid form to vapor form. The refrigerant path thermally couples the condenser to the evaporator. The refrigerant flows in bi-directions in the refrigerant path, driven by difference of densities of the refrigerant responsive to temperatures of the refrigerant within the refrigerant path, within the condenser, and within the evaporator.

The present disclosure also provides a method for cooling a rotating component. The method includes: pumping a refrigerant at least partial in liquid form to an evaporator and moving the refrigerant at least partial in vapor form to a condenser via the pumping such that a pressure of the refrigerant flowing into the evaporator is higher than another pressure of the refrigerant flowing into the condenser; absorbing a heat from an oil in the rotating component by the evaporator to evaporate the refrigerant from liquid form to vapor form; and cooling the refrigerant at least partial in vapor form via the condenser.

Other features and aspects will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description of the drawings refers to the accompanying figures in which:

FIG. 1 is a block diagram for a conventional cooling system applied on an air conditioner;

FIG. 2 is a simplified block diagram for a two phase oil cooling system applied on a work vehicle;

FIG. 3 is a block diagram of the first embodiment of FIG. 2 having multiple evaporators;

FIG. 4 is a block diagram of the second embodiment of FIG. 2 having a pump-condenser fan control logic;

FIG. 5 is a block diagram of the third embodiment of FIG. 2 having a separator separating a refrigerant in vapor form from the refrigerant in liquid form;

FIG. 6 is a block diagram of the fourth embodiment of FIG. 2 having a separator separating a refrigerant in vapor form from the refrigerant in liquid form, and the refrigerant in vapor form is processed in a compressor;

FIG. 7 is a block diagram of the fifth embodiment of FIG. 2, showing an evaporator is positioned within a rotating component;

FIG. 8A is a block diagram of the sixth embodiment of FIG. 2, showing an evaporator is positioned outside a rotating component;

FIG. 8B is a perspective view of the evaporator in FIG. 8A;

FIG. 9A is a block diagram of an embodiment of the two phase oil cooling system that utilizes antifreeze flowing through the evaporator and the heat exchangers positioned within the rotating components;

FIG. 9B is a block diagram of an embodiment of the two phase oil cooling system that utilizes antifreeze flowing through the evaporator and the heat exchangers positioned outside rotating components;

FIG. 10 is a block diagram of an embodiment of the two phase oil cooling system, where the rotating components are in partial parallel connection;

FIG. 11 is a block diagram of the seventh embodiment of FIG. 2, demonstrating the fan driven by the refrigerant; and

FIG. 12 is a block diagram of an embodiment of the two phase oil cooling system that utilizes buoyancy to drive the refrigerant flow.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, a conventional cooling system applied on an air conditioner includes an evaporator 14′, a compressor 24′, a condenser 12′, and a thermal expansion valve (TXV), where refrigerant flows through in liquid and/or in vapor form at different pressure. The air conditioner normally is fixed on a wall of a house and some elements of the air condition are indoor and some are outdoor. In general, the compressor 24′ and the condenser 12′ of the air conditioner are positioned in the outdoor environment; the thermal expansion valve (TXV) and the evaporator 14′ are positioned indoor environment. The evaporator 14′ is located in the low pressure side (compressor suction side) and the condenser 12′ is used in the high pressure side. The thermal expansion valve (TXV) is used between the condenser 12′ and the evaporator 14′ to reduce pressure.

In a path (suction line) between the evaporator 14′ and the compressor 24′, the refrigerant is at a low pressure and low temperature. In order to run the compressor 24′ properly, the refrigerant is in vapor form (gas or superheat gas). When the refrigerant reaches the compressor 24′, the compressor 24′ compresses the refrigerant in vapor form, such that the refrigerant in a path between the compressor 24′ and the condenser 12′ is at a high pressure (P_(H)) and high temperature (may be superheat). When the refrigerant reaches condenser 12′, the condenser 12′ cools the temperature of the refrigerant and change it into liquid form via a fan (not shown). The fan provides a first air flow AF_(1′) passing through a heat dissipation element of the condenser 12′ to remove the heat from the condenser 12′. Refrigerant at the exit of the condenser 12′ must be saturated or subcooled liquid for smooth operation of thermal expansion valve (TXV). In a path between the condenser 12′ and the thermal expansion valve (TXV), the refrigerant is still at the high pressure.

The thermal expansion valve (TXV) later collects the refrigerant from the condenser 12′. In the thermal expansion valve (TXV), the pressure of the refrigerant drastically decreases. The temperature of the refrigerant may also drop. Therefore, in a path between the thermal expansion valve (TXV) and the evaporator 14′, the refrigerant is at a low pressure (P_(L)). The low pressure refrigerant flows into the evaporator 14′. Another fan (not shown) adjacent to the evaporator 14′ provides a second air flow AF_(2′) (indoor) passing through a heat exchange element of the evaporator 14′. The heat of the second air flow AF_(2′) is absorbed by the refrigerant, because refrigerant in liquid form changing into vapor form requires latent heat (energy potential). Again, the refrigerant is discharged by the evaporator 14′ and flows into the compressor 24′.

FIG. 2 illustrates a simplified block diagram of a two phase oil cooling system 10 for a work vehicle. In particular, the two phase oil cooling system 10 is applied on at least one rotating component of the work vehicle, including transmissions, axles, e-machines, hydraulic pumps and motors. The two phase oil cooling system 10 comprises a condenser 12, an evaporator 14, and a pump 20. The condenser 12 is used to cool a refrigerant from vapor form to liquid form. The evaporator 14 is used to exchange heat between an oil of a rotating component of the work vehicle and the refrigerant. The two phase oil cooling system 10 also includes a refrigerant path 16 which has a first and second refrigerant paths 162, 164. The first refrigerant path 162 thermally couples the condenser 12 to the evaporator 14, and the second refrigerant path 164 thermally couples the evaporator 14 to the condenser 12. The refrigerant flows through the refrigerant path 16. The pump 20 is positioned in the first refrigerant path 162 for pumping the refrigerant from the condenser 12 to the evaporator 14, such that the evaporator 14 is downstream of the pump 20 and the condenser 12 is downstream of the evaporator 14. In other word, the pressure of the refrigerant in between the pump 20 and the evaporator 14 of the first refrigerant path 162 is high pressure P_(H); the pressure of the refrigerant in the second refrigerant path 164 is low pressure P_(L). The evaporator 14 is located in the high pressure side and the condenser 12 is located in the low pressure side. The reservoir, if any, is omitted in FIG. 2.

A first air flow AF₁ is driven by a condenser fan 80 to cool the condenser 12, such that the refrigerant in vapor form flowing from the second refrigerant path 164 can be transformed into liquid form. The pump 20 pumps the refrigerant into the evaporator 14. A first oil flow OF₁ flowing from or in the rotating component, transfers the heat to the refrigerant within the evaporator 14. With the vaporization of the refrigerant, the first oil flow OF₁ is therefore cooled. The heated refrigerant later exits from the evaporator 14 and enters to the condenser 12 to be liquidized.

The following embodiments include multiple variations derivative from FIG. 2. The embodiments of present disclosure can be modified and/or combined with at least one another to construe different configurations. The variations and the combinations will not depart from the spirit and scope of the present disclosure. For example, the pump 20 can be a two-phase flow pump, a positive displacement liquid pump, or can be combined with a compressor. The number of the evaporator 14 can be one or more than one. The multiple evaporators 14 can be applied on one or more rotating component. The position of the evaporator 14 can be inside or outside of the rotating component for exchanging the heat between the refrigerant and the oil.

Referring to FIG. 3, in the first embodiment of the present disclosure, the pump 20 is a two-phase flow pump, which has capability to pump the refrigerant in both vapor and liquid forms. Because pump 20 in this embodiment is compatible to the two forms of the refrigerant, it can avoid the cavitation that occurs when some the refrigerant in vapor form in a liquid pump. Therefore, even when the condenser 12 in this embodiment cannot completely transform the refrigerant in vapor form to liquid form, the pump 20 can still work smoothly to pump the refrigerant into the evaporators 14. There are multiple evaporators 14, each of which is applied on a respective one of rotating component (not shown in FIG. 3). In addition, in this embodiment, the first refrigerant path 162 divides a plurality of sub-first refrigerant paths 1622 and the second refrigerant path 164 divides a plurality of sub-second refrigerant paths 1642. Each of the evaporators 14 is coupled to one of the sub-first refrigerant paths 1622 and to one of the sub-second refrigerant paths 1642. Each of the sub-first refrigerant path 1622 is positioned a flow control valve 40 to control the flow in the respective one of the evaporators 14. In this regard, the four evaporators 14 may have different flows of the refrigerant and therefore the efficiency of the heat exchange in the evaporators 14 are different. Utilizing the flow control valves 40 can distribute appropriate amount of refrigerant in the evaporators 14. The control of the flow control valves 40 relates to the extent of necessity for the rotating components where the evaporators 14 are coupled. For one example, if one of the rotating components is a front axle and another one of rotating components is a rear axle, and if there is a mode change in the work vehicle, from four-wheel drive to front wheel drive, the flow control valve 40 applied on the front axle will increase the flow of the refrigerant, and the flow control valve 40 applied on the rear axle will decrease the flow of the refrigerant. The flow control valves 40 is operated via the command of a controller (not shown) which adjust the multiple flow control valves 40 based on the loading of the rotating components. For another example, if the temperature of one rotating component is higher than that of another, the flow control valve 40 allows larger flow of the refrigerant than another flow control valve 40 of another rotating component does. It can be performed when the flow control valves 40 are temperature control valves, or the flow control valves 40 coupled to thermometers and/or flow pressor sensor, in corporation with a controller (not shown) controlling the flow based on preset multiple criteria, including temperature, flow pressure, durability of the rotating components, etc. Alternatively, the multiple evaporators 14 can be applied on a single rotating component to cool different portions of the rotating component.

Referring to FIG. 4, it is the second embodiment of FIG. 2. The feature in this embodiment is similar to FIG. 3 except the pump 20 is a positive displacement liquid pump, and the two phase oil cooling system 10 also includes a controller 70 which has a pump-condenser fan control logic 72. The pump-condenser fan control logic 72 is connected to the pump 20 and condenser fan 80. To ensure most of the refrigerant exiting from the condenser 12 has been transformed into liquid form to prevent the cavitation occurred in the pump 20, the pump-condenser fan control logic 72 regulates the condenser 12 to cool the refrigerant before the pump 20 pumping the refrigerant. In this regard, the condenser 12 makes the refrigerant subcooled or saturated before the refrigerant reaches the pump 20.

Referring to FIG. 5, it is the third embodiment of FIG. 2. The pump 20 in this embodiment is a positive displacement liquid pump. The two phase oil cooling system 10 also includes a separator 22, a reverse refrigerant path 166, and a reverse flow control valve 42 positioned in the reverse refrigerant path 166. The separator 22 is positioned in the first refrigerant path 162 between the condenser 12 and the pump 20, and is configured to separate the refrigerant in vapor form from the refrigerant in liquid form and to permit the refrigerant in liquid form to flow through the pump 20. The remaining part of the refrigerant in vapor form flows through the reverse refrigerant path 166 from the separator 22 to the second refrigerant path 164. The reverse flow control valve 42, for example, a check valve, controls the flow of the refrigerant in vapor form in the reverse refrigerant path 166. The reverse flow control valve 42/check valve may be used to reduce the pressure in the separator 22 in case excessive refrigerant in vapor form build up. The refrigerant returns the second refrigerant path 164 will be cooled in the condenser 12 again. The reverse flow control valve 42 may be optional if the pump-condenser fan control logic 72 in the second embodiment applied to this embodiment. The reverse flow control valve 42 may be optional if the size of the condenser 12 is large enough.

It is noted that the features in the second and third embodiments can be combined (referring to FIGS. 4 and 5). The pump-condenser fan control logic 72 is connected to the pump 20 and condenser fan 80. The pump-condenser fan control logic 72 regulates the condenser 12 to cool the refrigerant before the pump 20 pumping the refrigerant. In this regard, the condenser 12 can cool the refrigerant before the refrigerant reaches the pump 20. Even if there is still a refrigerant in vapor form after the operation of the condenser 12, the refrigerant in vapor form will be separated by the separator 22 and returns the second refrigerant path 164 as described previously. The combination further prevents the pump 20 from cavitation when the pump 20 is a liquid pump.

Referring to FIG. 6, it is the fourth embodiment of FIG. 2. The pump 20 in this embodiment is a positive displacement liquid pump. The two phase oil cooling system 10 also includes a separator 22, a compressor path 1624 coupling the separator 22 to the first refrigerant path 162, and a compressor 24 positioned in the compressor path 1624. The compressor 24 compresses the refrigerant that is vapor form flowing from the separator 22 through the compressor path 1624 to the evaporators 14. The pump 20 pumps the refrigerant that is liquid form flowing from the separator 22 through the first refrigerant path 162 to the evaporators 14. In this embodiment, the compressor path 1624 later merges to the first refrigerant path 162, mixing the refrigerant in vapor and liquid forms. The compressor path 1624 is parallel to the first refrigerant path 162 from the separator 22 to the pump 20 such that the refrigerant in vapor form separated by the separator 22 does not flow into the pump 20 which is a liquid pump. In this regard, even if the rotating component is in high heat load and the condenser 12 cannot condense all the refrigerant into liquid form with the energy consumed by another component (i.g. energy recycling unit, introduced in next paragraph), the refrigerant in vapor form can be guided to the compressor path 1624 without damage the pump 20. Unlike the conventional cooling system as described in FIG. 1, where the refrigerant flows from the evaporator 14′, through the compressor 24′, to the condenser 12′, in this embodiment, the refrigerant (in vapor form) flows opposite direction, from the condenser 12, through the compressor 24, to the evaporator 14.

Referring again to FIG. 6, the two phase oil cooling system 10 includes an energy recycling unit 30 positioned in the second refrigerant path 164. In this embodiment, the energy recycling unit 30 is installed between the evaporators 14 and the condenser 12. The energy recycling unit 30 includes a turbine 32 driven by the refrigerant. The turbine 32 in this embodiment is a two phase flow turbine compatible to work with the refrigerant in vapor and liquid forms. The energy recycling unit 30 may include at least one of a secondary pump 34 and a generator 36 coupled to the turbine 32. The turbine 32 absorbs partial energy from the refrigerant and drives the secondary pump 34 and the generator 36. In one aspect, the turbine 32 can translate energy potential in the refrigerant that is vapor form into shaft power. The shaft power is used to turn the secondary pump 34 and the generator 36. In another aspect, the turbine 32 can also utilize the flow of the refrigerant, in liquid or vapor form, caused by the pump 20 to increase the shaft power. As such, the energy recycling unit 30 not only reuse excessive energy of the refrigerant but also share the task of the condenser 12 because a portion of the energy is removed. Therefore, more percentage of the refrigerant in liquid form is transformed into liquid form. Unlike the conventional cooling system as described in FIG. 1 having a thermal expansion valve (TXV) which may decrease the refrigerant flowing speed, the second refrigerant path 164 coupled to the condenser 12 and the evaporators 14 does not have to have the thermal expansion valve (TXV).

When the energy recycling unit 30 includes the secondary pump 34, the secondary pump 34 may pump another liquid to obtain additional functions. For example, the secondary pump 34 can be an oil pump 66 as shown in FIG. 8A. The secondary pump 34/oil pump 66 therefore can pump an oil from the rotating component 60, which will be introduced in detail later. Referring to FIG. 6, when the energy recycling unit 30 includes the generator 36, the generator 36 may be further coupled to a battery or other electrical components (not shown).

It is noted that, the energy recycling unit 30 can also be applied to the second refrigerant path 164 in the configuration of FIGS. 3-5 or other variations of FIG. 2.

With reference to FIG. 7, it is the fifth embodiment of FIG. 2. A rotating component 60 is used for illustration in this embodiment; however, the two phase oil cooling system 10 may have more than one rotating components 60. The evaporator 14 is at least partially submerged in the oil 62 within the rotating component 60 of the work vehicle. When the rotating component 60 operates, the oil 62 is driven to flow along at least one surface of the evaporator 14 to increase heat exchange rate. For example, the rotating component 60 is a front axle where a gear sets, a differential, a shaft, etc. are rotating and driving the oil 62 flowing quickly within the rotating component 60 and therefore such configuration improves the heat exchange between the refrigerant in the evaporator 14 and the oil 62 in the rotating component 60. The relative position between the evaporator 14 and the rotating component 60 can be applied to other variations of FIG. 2.

Referring to FIG. 8A, it is the sixth embodiment of FIG. 2. A rotating component 60 is used for illustration in this embodiment; however, the two phase oil cooling system 10 may have more than one rotating components 60. FIG. 8A merely demonstrates one evaporator 14 but the number of the evaporator 14, depending on practical design, can be numerous applied on single or multiple rotating components 60. In this embodiment, the evaporator 14 is positioned outside the rotating component 60. The two phase oil cooling system 10 further includes the oil pump 66, first oil path 642, and second oil path 644. The oil (will be shown in FIG. 8B) of the rotating component 60 is in fluid communication with the rotating component 60 and the evaporator 14 via the first oil path 642 and the second oil path 644 which couple the rotating component 60 to the evaporator 14. The oil pump 66 is positioned in the first oil path 642, and the oil pump 66 pumping the oil from the rotating component 60 to the evaporator 14. The two phase oil cooling system 10 may further include an oil filter 68 which can be positioned in either one of the first oil path 642 and second oil path 644. In this embodiment, the oil filter 68 is positioned in the second oil path 644. In this configuration, the flow of oil not only is not only cooled during the heat exchange in the evaporator 14, but is also cleaned during the filtration in the oil filter 68. Therefore, the oil exiting from the evaporator 14 is hot with impurity but when it flows back to the evaporator 14, it is cooled and clean.

The evaporator 14 is positioned outside the rotating component 60 makes an operator to maintain easily. The filtration process also extends the life of the rotating component 60. The sixth embodiment of the two phase oil cooling system 10 may be used in a work vehicle that normally has a severe duty application.

Referring to FIG. 8B, it illustrations a perspective view of the evaporator 14, with the refrigerant designated as 15 and the oil designated as 62. The evaporator 14 includes a refrigerant passage 142 through which flows the refrigerant 15. The refrigerant passage 142 thermally couples the first refrigerant path 162 to the second refrigerant path 164. The evaporator 14 also includes an oil passage 144 through which flows the oil 62. The oil passage 144 thermally couples the first oil path 642 to the second oil path 644. The refrigerant passage 142 and the oil passage 144 are at least in proximity to or engaged with one another to exchange heat. It is also noted that in at least a portion of the refrigerant passage 142 and in at least a portion of the oil passage 144, the refrigerant 15 and the oil 62 run in opposite directions.

Referring to FIG. 9A, it shows another embodiment of the two phase oil cooling system 10. Instead of circulating the refrigerant 15 around the work vehicle and exchanging heat directly with oil 62 at the evaporator 14, the two phase oil cooling system 10 may include one or more fluid (circuits) to absorb heat from the oil and to be cooled by the refrigerant 15. The condenser 12, the separator 22, the pump 20, the evaporator 14, and the refrigerant 15 may be similar to those as shown in FIG. 8. The rotating component in this embodiment includes a first rotating component 602, a second rotating component 604, and a third rotating component 606. The two phase oil cooling system 10 include a first heat exchanger 902, a second heat exchanger 904, and a third heat exchanger 906 respectively submerged in the oil of the first rotating component 602, the second rotating component 604, and the third rotating component 606. The two phase oil cooling system may also include an antifreeze path 94 which couples the evaporator 14 to the first, second and third heat exchangers 902, 904, 906. An antifreeze 92 is in fluid communication with the evaporator 14 and the first, second and third heat exchangers 902, 904, 906 via the antifreeze path 94. In addition, an antifreeze pump 96 is positioned in the antifreeze paths 94 and is configured to pump the antifreeze 92 to the evaporator 14.

The antifreeze 92 in this embodiment is glycol. The antifreeze 92 absorbs heat in the first, second, third heat exchangers 902, 904, 906 from the oil of the first, second, and third rotating components 602, 604, 606. The heated antifreeze 92 then flows to the evaporator 14 to heat the refrigerant from liquid form to vapor form such that the cooled antifreeze 92 can flow to the heat exchangers 902, 904, 906 again to cool the oil in the first, second, third rotating components 602, 604, 606.

Alternatively, referring to FIG. 9B, the first, second, third heat exchangers 902, 904, 906 are positioned outside the first, second, third rotating components 602, 604, 606. The oil is in fluid communication with the first, second, third heat exchangers 902, 904, 906 and the first, second, third rotating components 602, 604, 606. In this embodiment, there may be oil pumps (not shown) positioned in oil paths between the first, second, third heat exchangers 902, 904, 906 and the first, second, third rotating components 602, 604, 606. The oil pump can pump the oil from the rotating component. The oil is cooled in the heat exchangers 902, 904, 906 via the antifreeze 92.

In FIGS. 9A and 9B, the rotating components 602, 604, 606 are in series connection. The temperature of the antifreeze 92 increases when it flows from the first rotating component 602 to the third rotating component 606. Such arrangement may be based on heat transfer requirements and the maximum oil temperature requirements. For example, the first rotating component 602 may need to dissipate the heat quicker than the second and third rotating components 604, 606. For example, the third rotating component 606 may require the cooling fluid (i.e. antifreeze) above certain temperature to ensure the temperature of the oil is above certain temperature. Alternatively, based on the need, the rotating components 602, 604, 606 can be in parallel or partially parallel, as shown in FIG. 10.

Referring to FIG. 11, it is noted that the condenser fan 80 may be coupled to the refrigerant path 16. The condenser fan 80 is positioned in the second refrigerant path 164. In other words, the condenser fan 80 is downstream of the evaporator 14 but upstream of the condenser 12. Because the refrigerant, as described previously, is at least partially transformed to vapor form, the volumetric expansion of the refrigerant may be used to spin the condenser fan 80. In this regard, the fan 80 may spin without power from other sources or with relative lower power from other sources (not shown). This configuration may be applied to various embodiments having a path between an evaporator and a condenser.

Referring to FIG. 12, it illustrates another embodiment of the two phase oil cooling system 10 that utilizes buoyancy to drive refrigerant. In this embodiment, no pump 20 is required. Unlike previous embodiments that have pump 20 and the relative positions in height between the condenser 12 and evaporators 14 are flexible, in this embodiment the condenser 12 is positioned higher than the evaporators 14. In this embodiment, the two phase oil cooling system 10 comprises the condenser 12, the evaporators 14, the refrigerant path 16, the controller 70, and the condenser fan 80. The refrigerant path 16 thermally couples the condenser 12 to the evaporators 14. Because the temperature the refrigerant passing through or in proximity to the condenser 12 is lower than that of the refrigerant passing through or in proximity to the evaporators 14, the refrigerant passing through or in proximity to the condenser 12 moves downward and the refrigerant passing though or in proximity to the evaporators 14 moves upward. In this regard, the refrigerant is able to flow bi-directions in the refrigerant path 16. The refrigerant is driven by difference of densities of the refrigerant responsive to the temperatures of the refrigerant within the refrigerant path 16, within the condenser 12, and within the evaporators 14.

The two phase oil cooling system 10 further includes a temperature sensor 122 to measure the temperature of the refrigerant in at least one of the condenser 12, the evaporators 14, and the refrigerant path 16. In the embodiment as shown in FIG. 12, the temperature sensor 122 is positioned in the condenser 12 to measure the temperature of the refrigerant and to be electrically connected to the controller 70. The controller 70, based on the temperature of the refrigerant in the condenser 12, adjusts the condenser fan 80 operation speed. If the temperature of the refrigerant in the condenser 12 is relatively higher than its normal operation, the refrigerant exiting from the evaporators 14 may bring more heat, and the condenser fan 80 thus speeds up to provide the stronger first air flow AF₁ to ensure there is a substantial difference in density of the refrigerant between the condenser 12 and evaporators 14. In this regard, even without the pump as shown in the previous embodiment, the circulation of the refrigerant is ensured in this embodiment.

The present disclosure also provides a method for cooling a rotating component:

Step 1: pumping a refrigerant at least partial in liquid form to an evaporator and further to a condenser via a pump such that a pressure of the refrigerant flowing into the evaporator is higher than another pressure of the refrigerant flowing into the condenser.

When the pump is a liquid pump, step 1 also includes separating the refrigerant in vapor form from the refrigerant in liquid form to permit the refrigerant in liquid form to flow through the pump. The refrigerant in vapor form is disposed in two ways:

(1) diverting the refrigerant in vapor form back to the condenser through a reverse refrigerant path; or

(2) compressing the refrigerant in vapor form to the evaporator via a compressor.

Step 2: absorbing a heat from an oil of the rotating component by the evaporator to evaporate the refrigerant from liquid form to vapor form.

Step 2 also includes submerging the evaporator in the oil within the rotating component. In the operation of the rotating component, the oil is driven to flow along at least one surface of the evaporator to increase heat exchange rate.

Alternatively, step 2 includes pumping the oil by an oil pump from the rotating component to the evaporator to exchange the heat between the oil and the refrigerant. This step also includes filtering the oil via an oil filter utilizing the oil pressure created by the oil pump.

Step 2 may also include recycling energy from the refrigerant that exits from the evaporator. The turbine is driven by the refrigerant.

Step 3: cooling the refrigerant at least partial in vapor form via the condenser.

The steps mentioned above will repeat to cool the oil in the rotating component.

Without in any way limiting the scope, interpretation, or application of the claims appearing below, a technical effect of one or more of the example embodiments disclosed herein is to cool the oil in the rotating component with higher heat transfer coefficient refrigerant to reach better cooling performance. Another technical effect of one or more of the example embodiments disclosed herein is to distribute the heat loads from one or more rotating components without the oil being pumped to a remote distance of the work vehicle. Another technical effect of one or more of the example embodiments disclosed herein is to decrease the chance of oil leakage.

As used herein, unless otherwise limited or modified, lists with elements that are separated by conjunctive terms (e.g., “and”) and that are also preceded by the phrase “at least one of” or “one or more of” indicate configurations or arrangements that potentially include individual elements of the list, or any combination thereof. For example, “at least one of A, B, and C” or “one or more of A, B, and C” indicates the possibilities of only A, only B, only C, or any combination of two or more of A, B, and C (e.g., A and B; B and C; A and C; or A, B, and C)

While the above describes example embodiments of the present disclosure, these descriptions should not be viewed in a limiting sense. Rather, other variations and modifications may be made without departing from the scope and spirit of the present disclosure as defined in the appended claims. 

What is claimed is:
 1. A two phase oil cooling system for a work vehicle, comprising: a condenser configured to cool a refrigerant from vapor form to liquid form; an evaporator configured to exchange heat between a first fluid of the work vehicle and the refrigerant, thereby heating the refrigerant from liquid form to vapor form; a refrigerant path comprising a first refrigerant path thermally coupling the condenser to the evaporator and a second refrigerant path thermally coupling the evaporator to the condenser, the refrigerant configured to flow through the refrigerant path; and a pump positioned in the first refrigerant path for pumping the refrigerant from the condenser to the evaporator, such that the evaporator is downstream of the pump and the condenser is downstream of the evaporator.
 2. The two phase oil cooling system for a work vehicle of claim 1, wherein the first fluid is an oil of a rotating component of the work vehicle.
 3. The two phase oil cooling system for a work vehicle of claim 2, wherein the evaporator is at least partially submerged in the oil within the rotating component of the work vehicle.
 4. The two phase oil cooling system for a work vehicle of claim 3, wherein when the rotating component operates, the oil is driven to flow with turbulence over at least one surface of the evaporator to increase heat exchange rate.
 5. The two phase oil cooling system for a work vehicle of claim 2, wherein the evaporator is positioned outside the rotating component, and the oil of the rotating component is in fluid communication with the rotating component and the evaporator via a first oil path and a second oil path which couple the rotating component to the evaporator.
 6. The two phase oil cooling system for a work vehicle of claim 5, wherein the evaporator comprises a refrigerant passage through which flows the refrigerant and the refrigerant passage thermally couples the first refrigerant path to the second refrigerant path, and an oil passage through which flows the oil and the oil passage thermally couples the first oil path to the second oil path, and the refrigerant passage and the oil passage are at least in proximity to or engaged with one another to exchange heat.
 7. The two phase oil cooling system for a work vehicle of claim 6, comprising an oil pump positioned in the first oil path, and the oil pump pumping the oil from the rotating component to the evaporator.
 8. The two phase oil cooling system for a work vehicle of claim 7, comprising an oil filter positioned in one of the first oil path and the second oil path to filter the oil of the rotating component.
 9. The two phase oil cooling system for a work vehicle of claim 1, wherein the pump is a two-phase flow pump, pumping the refrigerant in liquid and vapor forms.
 10. The two phase oil cooling system for a work vehicle of claim 1, comprising a separator positioned in the first refrigerant path between the condenser and the pump and configured to separate the refrigerant in vapor form from the refrigerant in liquid form to permit the refrigerant in liquid form to flow through the pump.
 11. The two phase oil cooling system for a work vehicle of claim 10, comprising a reverse refrigerant path coupling the separator to the second refrigerant path, through the reverse refrigerant path flows the refrigerant in vapor form from the separator to the second refrigerant path.
 12. The two phase oil cooling system for a work vehicle of claim 11, comprising a reverse flow control valve positioned in the reverse refrigerant path.
 13. The two phase oil cooling system for a work vehicle of claim 10, comprising a compressor path coupling the separator to the first refrigerant path, and a compressor positioned in the compressor path, the compressor compressing the refrigerant that is vapor form flowing from the separator through the compressor path to the evaporator, and the pump pumping the refrigerant that is liquid form flowing from the separator through the first refrigerant path to the evaporator.
 14. The two phase oil cooling system for a work vehicle of claim 13, comprising an energy recycling unit positioned in the second refrigerant path, the energy recycling unit including a turbine driven by the refrigerant.
 15. The two phase oil cooling system for a work vehicle of claim 14, wherein the energy recycling unit comprises one of a secondary pump and a generator coupled to the turbine.
 16. The two phase oil cooling system for a work vehicle of claim 1, comprising an energy recycling unit positioned in the second refrigerant path, the energy recycling unit including a turbine driven by the refrigerant, and one of a secondary pump and generator coupled to the turbine.
 17. The two phase oil cooling system for a work vehicle of claim 2, comprising a flow control valve positioned in the first refrigerant path between the pump and the evaporator, the flow control valve operating based on a temperature of the oil.
 18. The two phase oil cooling system for a work vehicle of claim 17, comprising more than one of the evaporators and more than one rotating components having oils, wherein the first refrigerant path divides a plurality of sub-first refrigerant paths, the second refrigerant path divides a plurality of sub-second refrigerant paths, and each of the evaporators is coupled to one of the sub-first refrigerant paths and to one of the sub-second refrigerant paths and exchanges heat between oil of one of the rotating components and the refrigerant flowing through the evaporator.
 19. The two phase oil cooling system for a work vehicle of claim 18, comprising more than one flow control valves, each of which is positioned respective to one of the sub-first refrigerant paths, the flow control valves are configured to control the refrigerant flowing in the sub-first refrigerant paths.
 20. The two phase oil cooling system for a work vehicle of claim 1, comprising a condenser fan configured to cool the condenser and a pump-condenser fan control logic coupled to the pump and the condenser, and the pump-condenser fan control logic configured to regulate the condenser to cool the refrigerant before the pump pumping the refrigerant.
 21. The two phase oil cooling system for a work vehicle of claim 1, comprising a heat exchanger configured to exchange heat between the first fluid and an oil of a rotating component of the work vehicle.
 22. The two phase oil cooling system for a work vehicle of claim 21, wherein the first fluid is an antifreeze, the evaporator is positioned outside the rotating component, the first fluid is in fluid communication with the evaporator and the heat exchanger via an antifreeze path which couples the evaporator to the heat exchanger.
 23. The two phase oiling cooling system for a work vehicle of claim 22, further comprising an antifreeze pump positioned in the antifreeze paths and configured to pump the antifreeze to the evaporator.
 24. The two phase oiling cooling system for a work vehicle of claim 1, comprising a condenser fan configured to cool the condenser, the condenser fan positioned downstream of the evaporator and upstream of the condenser such that the condenser fan is at least partially driven by a volumetric expansion of the refrigerant.
 25. A two phase oil cooling system for a work vehicle, comprising: a condenser configured to cool a refrigerant from vapor form to liquid form; an evaporator positioned below the condenser and configured to exchange heat between an oil of a rotating component of the work vehicle and the refrigerant, thereby heating the refrigerant from liquid form to vapor form; and a refrigerant path thermally coupling the condenser to the evaporator, the refrigerant configured to flow in bi-directions in the refrigerant path, driven by difference of densities of the refrigerant responsive to temperatures of the refrigerant within the refrigerant path, within the condenser, and within the evaporator.
 26. A method for cooling a rotating component, comprising: pumping a refrigerant at least partial in liquid form to an evaporator and moving the refrigerant at least partial in vapor form to a condenser via the pumping such that a pressure of the refrigerant flowing into the evaporator is higher than another pressure of the refrigerant flowing into the condenser; absorbing a heat from an oil in the rotating component by the evaporator to evaporate the refrigerant from liquid form to vapor form; and cooling the refrigerant at least partial in vapor form via the condenser. 